Conventional signal analysis instruments, such as spectrum analyzers, oscilloscopes and the like, use triggering systems in order to trigger data capture of an input signal of interest for analysis by a user. However, more signal analysis applications require complicated triggering capability to detect transient or complex input signals, which conventional triggering systems cannot satisfy.
More particularly, a conventional triggering system has a signal level architecture. That is, there are different triggering blocks in the triggering system, and each triggering block detects a specified feature of the input signal, such as power level, spectrum shape, and the like. The input signal passes through only one of the triggering blocks to generate the corresponding trigger signal, so only one triggering condition can be used to detect the signal.
FIG. 1 is a block diagram illustrating a conventional triggering system of spectrum analyzer. Referring to FIG. 1, triggering system 100 receives an input signal and provides a trigger signal based on only one triggering function, selectable by switch 110. The trigger signal may be generated in response to External Trigger 120, which may be activated by the user, for example. No trigger signal will be generated in response to Free Run 130, which does not consider any trigger conditions and enables the input signal to pass through the triggering system. Alternatively, the trigger signal may be generated in response to a selected one of multiple trigger blocks 141 to 143 in trigger block set 140, each of which is configured to detect a corresponding trigger condition in the input signal. For example, trigger block 141 provides a time domain power level trigger, trigger block 142 provides a frequency domain power level trigger, and trigger block 143 provides a frequency mask trigger. However, as mentioned above, only one trigger may be selected at a time as the trigger signal. Further, the trigger blocks 141-143 may be predetermined, in that the user has a limited choice of corresponding functionalities.
Notably, some conventional triggering systems are able to implement more than one trigger (e.g., via multiple trigger blocks) with regard to an input signal. However, the trigger blocks are sequentially arranged, such that the input signal passes through all of the trigger blocks and a trigger signal is ultimately generated only once all of the corresponding trigger conditions are detected.
Thus, a disadvantage of conventional triggering systems is lack of flexibility. In contrast, in many signal analysis applications, the user would like to generate triggers based on complicated triggering conditions (for example, need to detect pulse signal with specified pulse duration and spectrum shape simultaneously), which cannot be resolved by a conventional single level triggering system. Also, even when multiple trigger blocks are available, the desired types and arrangements of various triggering conditions may not be accommodated, thus the conventional multiple level triggering system is likewise insufficient.